106 TESTACEOUS MOLLUSCA. 
gibbose, closed posteriorly, the rays spread all over the shell. 
4» » 13,.—Mazatlan. 
C. Raprara. Sow. Z. P. 1835. Sub- triangular, sub-equi- 
lateral, gibbous, rather pale, rayed and waved with itcceeal smooth, 
covered with a more or less thick horn-like epidermis ; the sides 
rounded towards the straightish ventral margin; no heart-shaped 
lunule ; four cardinal teeth. 2..23.—W. Columbia.—Very like 
Planulata, but the rays are composed of angulated markings. 
C. CrassaLELLoipEes.—Tricgona. C. Conrad. Journ. A. N. 
S. Phil. 7. p. 253. t. 19. f.17. Equilateral, triangular, transverse, 
thick, convex, depressed, whitish (often rayed with brown), lunule 
undefined ; anterior extremity truncated ; ligament short, very broad, 
and elevated; apex very prominent, beaks not oblique ; cardinal 
teeth very thick and prominent, anterior tooth elongated and thick, 
the sinus of the palleal scar angular. 7.— California. 
C. Sruttorum.—Tricona 8S. Gray in Analyst. 1838.— 
Donax 8. W.S.¢. 2. f. 2. Sub-triangular, oval, equilateral, con- 
vex, rather thick, smooth, glossy, rounded at the sides, ventral edge 
slightly arcuated ; variable in colouring, sometimes with a single 
central short white ray on a very pale livid ground, sometimes with 
broader or narrower livid rays on whitish ground: anterior slope 
livid : inside white, the lateral and posterior teeth connected. 
1..12.—Indian Seas? SS. America? 
C. Cosrara.—Venus C. Chemnitz f. 1975.—W. t. 7. f. 39. 
—D. p. 175.—Young.—C. Erycinetta. Lam. Oval, sub- 
cordate, white, with pale livid rays under a yellowish periostraca, 
thick, strong, glossy, with transverse broad well raised rather 
shelving ribs, which are flat above and about twice the breadth of 
the interstices : lunule elongated, heart-shaped, smooth, and as well 
as the anterior slope white lineated with livid red: anterior edge 
obtuse : inside uniform white. 13..23$.— Pacific ? — Closely allied 
to Erycina but more oval, its ribs distinct and its margin never 
as in that species stained with orange. 
C. Kinert.'—Venus K. Gray in W.S.f.9. Ovate, sub-cor- 
1 An orbicular and usually colourless group seems, with justice, 
to have been dissevered by Gray, Sowerby, &c. from ia genus we 
have been describing. 
ARTEMIS. —Po rt. 
Orbicular, edge entire; posterior tooth of the left valve rudimen- 
tary ; syphonal inflection angular, ascending, acute. 
The following species are described by Mr Gray in his valuable 
paper on the Cythereanze, in the Analyst for 1838. 
A. PonpEerosa. Gray. Orbicular, rather convex, very thick, 
